Bridge-connected relay



y 29, 1952' w. E. GLASSBURN 2,605,325

BRIDGE-CONNECTED RELAY Filed June 20, 1950 a 5 IQ 1 I: N I 1 I01 11 1 1 TIP 7 9. 3 6 l0 1 7 WITNESSES: L .2 INVENTOR William E. Glussburn.

fiwlo; I Fig.5. BY

ATTORNEY Patented July 29, 1952 UNITED STATES PATENT? OFFICE BRIDGE- CONNECTED RELAY William E. Glassburn, Bloomfield, N. J assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application June 20, 1950, Serial N 0. 169,259

6 Claims. 1

My invention relates to a wattmetric or product-type relay, and a bridge-network for energizing the windings of the relay from two inputcurrents of the same frequency. The bridge is preferably so designed that all of its legs have the same impedance. The relay is a producttype relay having two windings, defining a winding as an excitation-means for producing one of the two essential excitations or fluxes of the relay. A product-type relay develops a torque which is proportional to the product of the currents traversing the two windings, or excitationmeans, multiplied by a function of the phase- 2 cordance with a preferred form of embodiment of my invention;

Fig. 2 is a similar view showing a modification in which the two relay-windings are not subdivided, but the effect of subdivided windings is ob tained through the use of two mixing-transformers, one for each winding;

Fig. 3 is an equivalent circuit diagram of the essential energizing-connections of the relay angle between said currents. In a preferred embodiment of my invention, each of the windings is divided into the two equal parts, the two parts of each winding being connected in opposite legs of the bridge. The two input-currents are brought into the two diagonals of the bridge, so

operation or to move its rotor-member in the opposite direction, in response to the other input-current, which I designate the restraining current. These torques or responses of the relay are independent of the relative phase-angle between the two input-currents.

My invention is applicable both to high-speed relays and to slow-speed relays in which the speed of response varies significantly with the conditions which produce the relay-operation. My improved relay-assembly may be used either as a differential-current relay, or as a ratioor percentage-differential relay, or as an impedance relay, or in fact in any relay in which an operating torque and an opposing or restraining torque or force are required.

With the foregoing and other objectives in mind, my invention consists in the systems, circuits, combinations, apparatus, parts, and methods of design and operation, hereinafter described and claimed,- and illustrated in the accompanying drawing, wherein Figure 1 is a diagrammatic view of a Wattnietric relay-element in which each of the two relaywindings is split into two parts, the four parts being connected in a bridge-connection, in acshown either in Fig. 1 or in Fig. 2; and

Figs. 4, 5 and 6 are application-diagrams showing representative external circuit-connections for using my relay as a diiTerential-eurrent relay, a percentage-differential relay, and an impedance relay, respectively.

In Fig. 1, a wattmetric or product-type element is indicated at W, having two stationary windings or excitation-means W1 and W2. The relay winding W1 is subdivided into two equal parts I and 3, preferably with both of these parts equally distributed in all of the poles or windingslots of the relay. In like manner, the relaywinding W2 is subdivided into two parts 2 and 4. The relay-rotor is indicated at 5, and it is shown as carrying a contact-making member 6.

The four winding-parts l, 2, 3 and 4 are connected in a bridge-circuit having the corners m, n, o, p, with the winding I connected in the bridge-leg mn, the winding 2 connected in the next bridge-leg no, etc., as shown in Figs. 1 and 3. An input-circuit, having terminals 1 and 8, is provided, whereby an operating crrrent Io may be led into the corner m and out of the diagonally opposite corner 0 of the bridge. A second input-circuit, having terminals 9 and I0, is provided, whereby a restraining current Ir may be led into the corner n, and out of the diagonally opposite corner p of the bridge.

As shown in Fig. 1, a controlled circuit, having terminals l and I2, is also provided, in which the relay-contact 6 is connected, as is well understood in the relaying art.

In Fig. 2, an equivalent arrangement is provided, which avoids the necessity for subdividing each of the two relay-windings W1 and W2 into two separate winding-parts which are insulated from each other as well as from the frame of the relay, thus saving winding-space in the relay, at the expense of requiring two mixing-transformers M1 and M2. The transformer M1 has two primary windings l and 3 which are connected in the bridge-circuit as in Figs. 1 and 3, and one secondary winding S1 which is connected to the relay-winding W1. The other transformer M2 has two primary windings 2 and 4 which are connected in the bridge circuit in the same manner as in Figs. 1 and 3, and a secondary winding S2 which is connected to the relay-winding W2.

The equivalent energizing circuits are shown in Fig. 3, in which I have indicated that each of the two input-currents I and It divides equally, in passing through the bridge, because of the symmetry of the bridge-impedances. I have designated the currents which flow through the winding-portions I and 3 as each being half of the energizing-current I1 for the winding W1 so that the total exciting-current for the winding W1 may be regarded as the sum of thesetwo partcurrents, or I1, counting the winding W1 as having the same number of turns as either of its parts I and 3. A like convention is adopted for the currents in the other two winding-parts 2 and 4, as indicated by the designation .512, applied to the corresponding arrows in Fig. 3. The subdivided operating-currents .510 and the subdivided restraining currents .511 are also indicated by suitable arrows in Fig. 3,,from which it is apparent that the total energizing-current 11 for the relay-winding W1 is equal to the difference between the two input-currents, or (I0-Ir), while the total relay-current I2 for the other relay-winding W2 is. equal to the sum of the two input-currents, or (Io-Hr) I use a dot over a symbol to indicate a complex number, whereas the symbol without the dot represents either the vector generally, without reference to its phase-angle, or the scalar or absolute-magnitude value of the vector, in accordance with a familiar convention.

In explaining the design and operation of my relay, I will assume thatthe relay is energized by the relay-currents I1 and 12 having a phaseangle between them, andthat the-relay develops a torque T=I1I2 cos -q (l) where q is an angle which ischaracteristic oi the relay.

If, now, the two.energizing-currents are I1=I[)-IrL0 I2=IU+ITLO (3) where 0 is the angle by which the restraining current Ir leads the operating current 10, the total relay-torque will be the sum of the products of the different pairs of terms, each multiplied by cos (oq), where qfzo is the angle between the two terms being multiplied. The torque is therefore T=Io cos (1+IOIr cos (0-q)-IcI1- cos (Ii-q) IT cos q:(IO Ir cos (4) This proves that the relay-torque has an operative or relay-actuating component, I 0 cos q, which is dependent upon the square of the operating current 10, and the characteristic responseangle 13/ of the relay; while the relay-torque has a restrainin or response-opposing component, fr cos c, which is dependent upon the square of the restraining current Ir, and the characteristic response-angle q of the relay. The phaseangle 0 of the restraining current relative to the operating current makes no difference in the response of the relay.

Various uses or applications may be made of my novel relay-assembly, three illustrative examples being indicated, in simple forms, in Figs. 4, 5 and 6.

In Fig. 4, external connections are shown,

which make use of my relay as a differentialcurrent relay, which is used to compare the magnitudes of the currents in two feeders l3 and M which are connected to a common bus IS in an alternating-current distribution-system. The input-current I0 is supplied to the relay from a line-current transformer CT13 in the feeder l3, while the other input-current Ir is supplied. to the relay from a line-current transformer GT1 x in the feeder l4. Since my relay develops a torque in one direction in response to the first input-current I0, and a torque in the opposite direction in response to the second input-current Ir, my relay can thus be used in the same manner as any other current-differential relay.

Fig. 5 shows illustrative external connections for using my invention in the percentage differential protection of a three-phase generator G. Two line-current transformers GT1 and GT2, on opposite sides of the generator, are connected together through the primary winding 15 of a restraint-transformer II, this transformer having a secondary winding [3 which produces a restraint-current Ir which is equal to half of the sum of the currents traversing the two currenttransformers GT1 and GT2. The primary winding [6 of the restraint-transformer is provided with a midtap 20, which is connected to the common terminal 2! of the currenttransformers, through the primary winding 22 of an operating transformer 23. The operating transformer 23 has a secondary winding 24 which energizes my relay with an operating current Io whi h is proportional to the difference between the lino-currents flowing in the ourrent-transformers GT1 and GT2. The operating transformer 23 may, or may not, be saturaole: if it is saturable it gives the relay the well-known variable percentage character istic.

Fig. 6 shows the external connections which illustrate the use of my relay as an impedance relay, or a voltage-restraint overcurrent relay, in which the operating current In is derived from a line-current transformer ST in a protected alterhating-current line-section 25, while the restraining current Ir is provided by a line-energized potential-transformer so that said restraining current is proportional to the linevoltage. In order to make the design flexible in its use and adjustment for special applications, it is preferable to provide means for adjusting the magnitude of one or both of the input-currents I0 and Ir, as by means of a variable-ratio auxiliary transformer 21 in the line-current-responsive input-circuit, and a potentiometer 2%} in the line-voltage-responsive input-circuit.

The three application-diagrams of 4, 5 and 6 are intended to be only the simplest sort or" diagrams, each illustrative of its particular type of service. It will be understood, of course. that various other external connections may be used. It should be understood, also, that my invention is applicable alike to high-speed relays and slow-speed or time-element relays.

Various modifications and substitutions may be made by those skilled in the art, without departing from the essential spiritof my invention. I desire, therefore, that the appended claims shall be accorded the broadest construction consistent with their language.

I claim as my invention:

1. A product-responsive relayin element having two excitation-means, energi rig-means for providing two energizing-circuits :for energizing each of said excitation-meansand a bridge-circult connection for the four energizing-circuits, the two energizing-circuits for each excitationmeans being connected in opposite legs of the bridge, said bridge-circuit including two inputcircuits connected to the respective diagonal corners of the bridge, whereby one of said excitationmeans is effectively energized responsively to a sum-function of the two input-currents, while the other excitation-means is effectively energized responsively to a difference-function of the two input-currents.

2. A product-responsive relaying element having two excitation-means of substantially identical impedances, energizing-means for providing two substantially equal energizing-circuits for energizing each of said excitation-means, and a bridge-circuit connection for the four energizing-circuits, the two energizing-circuits for each excitation-means being connected in opposite legs of the bridge, said bridge-circuit including two input-circuits connected to the respective diagonal corners of the bridge, whereby one of said excitation-means is efietively energized responsively to the sum of the two input-currents, while the other excitation-means is effectively energized responsively to the difference between the two input-currents.

3. A product-responsive relaying element having two excitation-means, each excitation-means having two winding-parts, and a bridge-circuit connection for the four winding-parts, the two winding-parts of each excitation-means being connected in opposite legs of the bridge, sai'd bridge-circuit including two input-circuits connected to the respective diagonal corners of the bridge, whereby the two parts of one of said excitation-means are energized responsively to a sum-function of the two input-currents, while the two parts of the other excitation-means are energized responsively to a difference-function of the two input-currents.

4. A product-responsive relaying element having two excitation-means of substantially identical impedances, each excitation-means having two substantially identical winding-parts, and a bridge-circuit connection for the four winding-parts, the two winding-parts of each excitation-means being connected in opposite legs of the bridge, said bridge-circuit including two input-circuits connected to the respective diagonal corners of the bridge, whereby each of the two parts of one of said excitation-means is ener- 6 gized by substantially one-half of the sum of the two input-currents, while each of the two parts of the other excitation-means is energized by substantially one-half of the difference between the two input-currents.

5. A product-responsive relaying element having two windings, a mixing transformer for energizing each of said windings, each mixing transformer having a secondary winding connected to its relay-winding, and having two primary windings, and a bridge-circuit connection for the four primary windings, the two primary windings of each mixing transformer being connected in opposite legs of the bridge, said bridge-circuit including two input-circuits connected to the respective diagonal corners of the bridge, whereby one of said relay-windings is energized responsively to a sum-function of the two input-currents, while the other relay-winding is energized responsively to a difference-function of the two input-currents.

6. A product-responsive relaying element having two windings of substantially identical impedances, two substantially identical mixing transformers for energizing the respective relaywindings, each mixing transformer having a secondary winding connected to its relay-windings, and having two substantially identical primary windings, and a bridge-circuit connection for the four primary windings, the two primary windings of each mixing transformer being connected in opposite legs of the bridge, said bridgecircuit including two input-circuits connected to the respective diagonal corners of the bridge, whereby each of the primary windings of one of said mixing transformers is energized by substantially one-half of the sum of the two inputcurrents, while each of the two primary windings of the other mixing transformer is energized by substantially one-half of the difference between the two input-currents.

WILLIAM E. GLASSBURN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,208,907 Leyburn July 23, 1940 2,426,033 Lenehan Aug. 19, 1947 

